OBJECTIVE: To determine the proportion of asthma patients with a poor perception of dyspnea, correlating the level of that perception with the severity of acute bronchoconstriction, bronchial hyperresponsiveness, use of maintenance medication, and asthma control. METHODS: Uncontrolled clinical trial involving asthma patients treated at the Pulmonology Outpatient Clinic of the São Lucas Hospital, in Porto Alegre , Brazil. Methacholine challenge testing was performed using a five-breath dosimeter protocol. The perception of dyspnea after each breath was determined using the Borg scale. Data concerning asthma control, medication in use, and use of rescue short-acting bronchodilators were recorded. RESULTS: Of the 65 patients included in the study, 53 completed the evaluation. Of those, 32 (60.5%) showed adequate perception of dyspnea after the methacholine challenge test, whereas 21 (39.5%) did not perceive any changes in the degree of dyspnea even after a 20% fall in FEV1. There were no significant differences between the two groups regarding baseline FEV1, percentage fall in FEV1, and the dose of methacholine causing a 20% fall in FEV1. The perception of dyspnea was not significantly associated with age (p = 0.247); gender (p = 0.329); use of maintenance medication (p = 0.152); asthma control (p = 0.562), bronchial hyperresponsiveness (p = 0.082); or severity of acute bronchoconstriction (p = 0.749). CONCLUSIONS: A significant proportion of asthma patients have a poor perception of dyspnea. The factors related to the inability of these patients to identify changes in pulmonary function have not yet been well defined. In order to reduce asthma-related morbidity and mortality, it is essential that this group of patients be identified and counseled.
Asthma; Dyspnea; Airway obstruction
